18.05.13 Summary of ultrasound findings and chromsome abnormalities

Question 1

What are the three major groups of foetal abnormality?

Answer 1

1. Neural tube defects
   2) Chromosome abnormalities
   3) Congenital Heart Defects

Question 2

What are the aims of first trimester ultrasound examination? When can this be performed?

Answer 2

11+2/40 - 14+1/40

1) Check the viability of the pregnancy
2) dating
3) Identified multiple regnancies
4) Placental localization
5) Detecting foetal anomalies

Question 3

What is the single most powerful marker available today for differentiating Down syndrome pregnancies from euploid pregnancies?

Answer 3

First timerster measurement of the foetal nuchal translucency space (NT); the subcutaneous collection of fluid under the skin of the foetal neck. >3.5mm deemed significant.
Allows detection of 75-80% of fetuses with aberrant karyotype.

Question 4

What are the possible causes of a raised NT? How can a raised NT progress?

Answer 4

1) Cardiac failure due to secondary or structural malformation
2) Abnormal or delayed development of the lymphatic system

Can progress into nuchal oedema, cystic hygroma or foetal hydrops in the second trimested.

May regress

Question 5

A raised NT is associated with an increased risk of chromosomal disorders. Which are the most common?

Answer 5

T21, T18, T13 and Turner syndrome (respectively).

Tripoloidy - less common

Question 6

Give some examples of structural malformations can be detected in the first trimester ultrasound scan?

Answer 6

Absent nasal bone
Regurgitant flow across tricuspid valve (Doppler evaluation of foetal ductus venosus)
Holoprosencephaly
Omphalocele
Megacystis
Limb abnormalities

Question 7

What can a Doppler evaluation of the foetal ductus venosus show? What association does this have with chromosome aneuploidy?

Answer 7

Doppler evaluation of foetal ductus venosus - regurgitant flow across the tricuspid valve is associated with aneuploidy and foetal cardiac malformations (75% of T21 vs 7% chromosomally normal).

Question 8

What can be detected during nasal bone sonography? What association does this have with chromosome abnormalities?

Answer 8

Nasal bone presence/absence - not visible in 60-70% of T21, 55% of T18 and 34% T13 (may not be seen in 2% of abnormal)

Question 9

What is holoprosencephaly? What is its association with chromosome abnormalities?

Answer 9

Physiological failure of the brain to divide into lobes or hemispheres. 30% of cases will have a chromosome abnormality. 
T13
T18
7q36 
SSH gene at 7q36 responsible for HPE

Question 10

What is omphalocele? What is its association with chromosome aneuploidy?

Answer 10

Herniation of the foetal abdominal contents due to the physiological failure of the abdomen to close around the umbilical cord.

60% from 12 weeks scan will have a chromosome abnormality (35% in mid-gestation due to high rate of IUD).

T13
T18
Beckwith-Wiedemann

Question 11

What is megacystis? What chromosome abnormalities can it be associated with?

Answer 11

Enlarged foetal bladder due to ureteric obstruction.

T13
T18

Question 12

Give some examples of limb abnormalities that can be detected on the first trimester scan and the chromosomal abnormalities they are associated with.

Answer 12

Relative shortening of the long bones: T21, T18, triploidy and Turner syndrome

Syndactyly is associated with triploidy

Clinodactyly and sandal gap - T2

Polydactyly - T13

Overlapping fingers, rocker-bottom feet, talipes - T18

Question 13

When can a mid-trimester foetal anomaly scan be performed?

Answer 13

18+0/40 - 20+6/40

Question 14

Give five possible scan findings in a 2nd trimester T21 pregnancy?

Answer 14

25% of second trimester T21 pregnancies will have major congenital anomalies detectable by ultrasound.

1) Brachycephaly
2) Nail hypoplasia
3) Nuchael oedema
4) Cardiac defects (mainly AVSDs, ToF)
5) Intracardiac echogenic foci
6) Duodenal atresia (30% with have T21)
7) Echogenic bowel
8) Sandal gap
9) Clinodactyly of the fifth finger
10) Transverse palmar crease
11) Hydrops
12) IUGR
13) Renal anomalies
14) Syndactyly

Question 15

Give five possible scan findings in a 2nd trimester T18 pregnancy?

Answer 15

1) Choroid plexus cyst
2) Absent corpus callosum
3) Enlarged cisterna magna
4) Facial cleft
5) Micrognathia
6) Nuchael oedema
7) Heart defects e.g. VSD
8) Horeshoe kidney and other renal defects
9) Diaphragmatic hernia
10) Oesophageal atresia
11) Exomphalos
12) Single umbilical artery
13) Echogenic bowel
14) IUGR
15) Overlapping fingers, talipes/rocker-bottom feet
16) Substantially decreased placental volume
17) Neural tube defects
18) Radial hypoplasia

Question 16

Give five possible scan findings in a 2nd trimester T13 pregnancy?

Answer 16

1) Holoprosencephaly +/- cleft lip/palate
2) IUGR
3) Microcephlay
4) Cardiac (AVD or VSD)
5) Renal abnormalities and often large and echogenic kidneys
6) Exomphalos
7) Post-axial polydactyly

Question 17

What kind of triploidy may continue past 20 weeks? What are some indications of this type of pregnancy on the 2nd trimester scan?

Answer 17

Diandy - rarely past 20 weeks
Digyny - may persist into the third trimester. Placenta is thin and the foetus shows:
1) severe asymmetrical growth restriction
2) Mild ventriculomegaly
3) Micrognathia
4) Cardiac abnormalities
5) Myelomenigocoele
6) Syndactly
7) Hitch-hiker toe deformity
8) Holoprosencephaly
9) Dandy-Walker malformation

Question 18

What are the common indications of a Turner syndrome pregnancy on 2nd trimester scan?

Answer 18

Large nuchal cystic hygroma.

75% of foetus with cystic hygroma will have a chromosome abnormality and 95% of these is Turner syndrome.

Generalised oedema
Mild pleural effusions and ascites
Cardiac abnormalities
Horseshoe kidney
Hydrops
IUGR

Question 19

What features may indicated mosaic trisomy 2 on a 2nd trimester scan?

Answer 19

1) absent gall bladder
2) Talipes
3) Renal cysts

Question 20

What features may indicated mosaic trisomy 7 on a 2nd trimester scan?

Answer 20

1) Low set ears
2) Talipes/rocker-bottom feet
3) Clitoromegaly
4) Renal agenesis

Question 21

What features may indicated mosaic trisomy 8 on a 2nd trimester scan?

Answer 21

1) Skeletal anomalies
2) Cardiac defects
3) Renal abnormalities

Question 22

What features may indicated mosaic trisomy 9 on a 2nd trimester scan?

Answer 22

1) IUGR
2) Microphthalmia
3) Cardiac defects
4) Vermis hypoplasia
5) Enlarged renal cysts

Question 23

What chromosome abnormality is associated with Pallister-Killian syndrome. What are the possible prenatal indications of this syndrome?

Answer 23

Mosaic tetrasomy 12p

1) Congenital diaphragmatic hernia
2) Short limbs
3) Abnormal hands and feet

Question 24

What chromosome abnormality is associated with Wolf-Hirschhorn syndrome. What are the possible prenatal indications of this syndrome?

Answer 24

4p16. 3 deletion
1) IUGR
2) Microcephaly
3) Cleft lip
4) Heart defects

Question 25

What chromosome abnormality is associated with Cri-du-chat syndrome. What are the possible prenatal indications of this syndrome?

Answer 25

5p15 deletion

1) CHD
2) Cleft lip and palate

Question 26

What chromosome abnormality is associated with Miller-Dieker syndrome. What are the possible prenatal indications of this syndrome?

Answer 26

17p13.3 deletion

Lissencephaly

Question 27

What chromosome abnormality is associated with Williams syndrome. What are the possible prenatal indications of this syndrome?

Answer 27

7q11. 23 deletion
1) IUGR
2) Nasal bone hypoplasia
3) Cardiac defects

Question 28

What chromosome abnormality is associated with Di-George syndrome. What are the possible prenatal indications of this syndrome?

Answer 28

22q11. 2 deletion
1) Cardiac defects (particularly outflow tract defects, ToF)2) Renal abnormalities
3) IUGR
4) Polyhydramnios
5) Cleft lip and palate
6) Thymic hypoplasia

Question 29

What genetic/chromsome abnormality is associated with Roberts syndrome. What are the possible prenatal indications of this syndrome?

Answer 29

ESCO2 gene can be tested where mutations are known. PCS on solid stain chromosome preps.

1) Severe limb shortening (upper limbs more affected)
2) Oligodactyly
3) Thumb aplasia
4) Cleft lip
5) Cystic kidneys.

Question 30

What are some prenatal SCAN indications of UPD?

Answer 30

UPD7mat (SRS) asymmetrical growth restriction

UPD11pat (BWS) Overgrowth in association with omphalocele

UPD14mat - small thorax and polyhydramnios

Question 31

What are the antentally detectable songraphic features of achondroplasia?

Answer 31

May not be detectable until the 3rd trimester

1) Short femur length measurement <5th centil
2) Trident hand - 2,3,4 fingers similar in length
3) Frontal bossing